Hydrogenation catalysts for polysilanes are well known in the art. These include both metals and metal salts, which are insoluble in the polysilane reactants, and metal complexes containing organic ligands, which are soluble in the polysilane reactants. However, hydrogenation catalysts disclosed in the prior art generally contain palladium, ruthenium, rhodium, platinum or nickel. Although copper metal, copper salts and copper complexes are well known as catalysts for a wide variety of reactions, most of which are oxidative in nature (see L. F. Fieser and M. Fieser, Reagents For Organic Synthesis, pp. 155-170 (1967)) they have not been considered to be useful as hydrogenation catalysts unless combined with chromium.
For example, U.S. Pat. No. 3,639,105 discloses the preparation of hydrosilanes from alkyl-substituted disilanes and halogen-substituted disilanes by hydrogenation of the disilane at a temperature of from 25.degree. C to 250.degree. C in the presence of a catalyst. The catalysts useful in the process of that patent are Group VIII transition metal catalysts, including organophosphine complexes of those transition metals.
Another publication (see H. Gilman and G. L. Schwebke, "Advances in Organometallic Chemistry", 1, 89 (1964)) discloses the hydrogenation of an unusual cyclic tetraphenyltetrasilane using an initial hydrogen pressure of 800 psi and a reaction temperature of 150.degree. C using a copper chromite catalyst. At the same reaction conditions, hexaethyldisilane failed to cleave. No disclosure was made of the use of a copper catalyst without chromium. The reactivity of halogen-containing polysilanes was not investigated.
Another publication (Chemical Abstracts, 53, 17888 (1959)) discloses the cleavage of the Si-Si bond in methylchlorodisilanes using disilanes in the vapor phase over 5% KOH/Al.sub.2 O.sub.3 at 500.degree. C to give monosilanes.